This invention relates to a signal converter, particularly to a signal converter in which a certain input signal, such as a voltage signal from a temperature sensor, a position detector, a techogenerator or the like, can be converted into an output signal in an absolute value substantially proportional to the difference between the input signal and a predetermined reference.
There is often the need for conversion of a signal to absolute value in various applications. In the case, for example, where a detected signal which changes both in the negative and the positive ranges is indicated in digital form, it is necessary that the absolute value of the detected signal and the sign thereof are provided. The absolute value in analog form is converted into a signal in the digital form, and the converted signal and the negative or positive sign are separately indicated by means of respective indicators.
Signals of such nature may represent, for example, a varying temperature, a position detecting signal, a speed difference signal from a predetermined reference and the like. For easy understanding of this invention, the following description will relate to temperature indications.
Various known temperature sensors have either a monotonously incremental characteristic or a monotonously decremental one in relationship of a detected output voltage to a temperature to be detected; for example, the Temperature Sensitive Resistor TSR 5-1001F (made by Corning Co., U.S.A.) has such an incremental characteristic, and a known thermistor element has such a decremental characteristic. Therefore, in order to produce a signal corresponding to the absolute value of the detected temperature, it is necessary to provide a signal converter which exhibits a decremental characteristic in a range of minus temperature and an incremental characteristic in a range of plus temperature with the boundary at 0.degree. C. Such a conventional signal converter has two amplifiers. One of the amplifiers has a decremental characteristic and is used for the range of minus temperatures and the other has an incremental characteristic and is used for the range of plus temperatures. The two amplifiers are switched over to each other with the boundary at 0.degree. C. The signal converter of this type has the disadvantage that the two amplifiers are necessary, whereby the converter has a large number of components and is therefore expensive.